Method and system for providing reliable communication with redundancy for energy constrained wireless systems

ABSTRACT

A method and apparatus is provided to supervise a network, in which a first device supervises a network node element, and a second device partially supervises the network node element.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent applications entitled “Methodand System for Time Synchronization in Communication Networks” (AttorneyDocket No. 11403/5501), “Method and System for Providing AcknowledgedBroadcast and Multicast Communication” (Attorney Docket No. 11403/5502),“Method and System for Providing an Energy Efficient Exchange ofInformation in Wireless Networks” (Attorney Docket No. 11403/5503),“Method and System for Providing Interference Avoidance and NetworkCoexistence in Wireless Systems” (Attorney Docket No. 11403/5504),“Method and System for Reliable Data Transmission in Wireless Networks”(Attorney Docket No. 11403/5505), “Method and System to Reduce Delayand/or Energy Consumption in a Multi-Hop Wireless System” (AttorneyDocket No. 11403/5506), “Method and System for Providing a Modified TimeDivision Multiple Access (TDMA) for Reduced Delay” (Attorney Docket No.11403/5507), “System and Method for a Communication Protocol forWireless Sensor Systems Including Systems with High PriorityAsynchronous Message and Low Priority Synchronous Message” (AttorneyDocket No. 11403/5509), “Method and System to Reconfigure a Network toImprove Network Lifetime Using Most Reliable Communication Links”(Attorney Docket No. 11403/5510). The disclosure of each of theforegoing related applications is hereby incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a method and system for supervisingenergy constrained network node elements of a wireless network.

BACKGROUND

In certain communication systems it may be required that every node inthe system be supervised to make sure it is operational and cancommunicate with other devices and/or other network elements. Sincecommunication may be resource expensive, each device may be supervisedby only one other device. However, if this other device malfunctions,then it may be difficult to determine the status of the devices that aresupervised by the malfunctioning device. This problem may be handled,for example, by having redundancy, but such redundancy may requireadditional resources and/or complexity.

In certain wireless communication systems, transmitting is more energyexpensive than receiving, or in other words, transmitting is more“energy hungry” than receiving, that is, on average it may require moreenergy to transmit messages than to receive messages. If, for example,the wireless media is a broadcast media then the transmitting devicemust ensure that its transmission is received by all intended receiverdevices when these receiver devices are ready and able to receive thetransmission, whereas the receiver devices may merely be required tolisten and receive the transmission with minimal expended energy.

SUMMARY OF THE INVENTION

An exemplary embodiment and/or exemplary method of the present inventionprovides a method and system for improved efficiency for networksupervision, including, for example, network supervision of energyconstrained devices of a network system. The present invention may beused, for example, in wired or wireless systems.

According to an exemplary embodiment and/or exemplary method of thepresent invention, each device of a network is supervised by a firstdevice and partially supervised by a second device. Having an additionaldevice to “partially” supervise the first device, rather than “fully”supervise the first device may be more resource efficient. In thisregard, the additional device may be configured, for example, only toreceive and forward any error messages with other messages theadditional device is otherwise configured and/or required to send. Theadditional device may also be configured not to acknowledge or forwardany other non-error message of the device it is partially supervising.

An exemplary embodiment and/or exemplary method of the present inventionis directed to an apparatus to supervise a network, which includes afirst device to supervise a network node element, and a second device topartially supervise the network node element.

Another exemplary embodiment and/or exemplary method of the presentinvention is directed to an apparatus to supervise a network, in whichthe second device forwards an error message transmitted by the networknode element to a higher level node in the network if the first devicedoes not forward the error message.

Yet another exemplary embodiment and/or exemplary method of the presentinvention is directed to an apparatus to supervise a network, in whichthe second device ignores non-error message from the network nodeelement.

Still another exemplary embodiment and/or exemplary method of thepresent invention is directed to an apparatus to supervise a network, inwhich the second device appends the error message to a another message.

Yet another exemplary embodiment and/or exemplary method of the presentinvention is directed to an apparatus to supervise a network, in whichat least one of the first device, the second device, the network nodeelement, and the higher level are energy constrained devices.

Still another exemplary embodiment and/or exemplary method of thepresent invention is directed to an apparatus to supervise a network, inwhich at least one of the first devices, the second device, the networknode element, and the higher level node are energy constrained wirelessdevices.

Yet another exemplary embodiment and/or exemplary method of the presentinvention is directed to an apparatus to supervise a network, in whichthe second device is configured to supervise another network nodeelement.

Still another exemplary embodiment and/or exemplary method of thepresent invention is directed to an apparatus to supervise a network, inwhich the first device is configured to partially supervise anothernetwork node element.

Yet another exemplary embodiment and/or exemplary method of the presentinvention is directed to an apparatus to supervise a network, in whichthe second device is configured to supervise another network nodeelement and the first device is configured to partially supervise theanother network node element.

An exemplary embodiment and/or exemplary method of the present inventionis directed to a method of supervising a network node element, themethod including providing a first device to supervise a network nodeelement, and providing a second device to partially supervise thenetwork node element,

Another exemplary embodiment and/or exemplary method of the presentinvention is directed to a method of supervising a network node element,the method including polling, by the first device, a status of thenetwork node element, and forwarding, by the second device, an errormessage transmitted by the network node element to a higher level nodein the network if the first device does not forward the error message.

Yet another exemplary embodiment and/or exemplary method of the presentinvention is directed to a method of supervising a network node element,the method including ignoring, by the second device, non-error messagesfrom the network node element.

Still another exemplary embodiment and/or exemplary method of thepresent invention is directed to a method of supervising a network nodeelement, the method including appending, by the second device the errormessage to another message.

Yet another exemplary embodiment and/or exemplary method of the presentinvention is directed to a method of supervising a network node element,the in which at least one of the first device, the second device, thenetwork node element, and the higher level are energy constraineddevices.

Still another exemplary embodiment and/or exemplary method of thepresent invention is directed to a method of supervising a network nodeelement, in which at least one of the first devices, the second device,the network node element, and the higher level node are energyconstrained wireless devices.

Yet another exemplary embodiment and/or exemplary method of the presentinvention is directed to a method of supervising a network node element,in which the second device is configured to supervise another networknode element.

Still another exemplary embodiment and/or exemplary method of thepresent invention is directed to a method of supervising a network nodeelement, in which the first device is configured to partially superviseanother network node element.

Yet another exemplary embodiment and/or exemplary method of the presentinvention is directed to a method of supervising a network node element,in which the second device is configured to supervise another networknode element and the first device is configured to partially supervisethe another network node element.

An exemplary embodiment and/or exemplary method of the present inventionis directed to a method of supervising a network node element, themethod including aggregating, by the first device, non-error messagesfrom the network node element.

An exemplary embodiment and/or exemplary of the present invention isdirected to a method of supervising a network node element, the methodincluding providing a first device to supervise a network node element,providing a second device to partially supervise the network nodeelement, polling, by the first device, a status of the network nodeelement; aggregating, by the first device, non-error messages from thenetwork node element, forwarding, by the second device, an error messagetransmitted by the network node element to a higher level node in thenetwork if the first device does not forward the error message,appending, by the second device, the error message to another message,and ignoring, by the second device, non-error messages from the networknode element, in which at least one of the first device, the seconddevice, the network node element, and the higher level are energyconstrained wireless devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows exemplary network node elements of a wireless network, inwhich one network node element supervises another network node element.

FIG. 2 shows an exemplary multihop network, which includes a basestation and node elements arranged in a hierarchical manner to show asupervisory relationship between the base station and the networkelement nodes, and between the network node elements themselves.

FIG. 3 shows an exemplary multihop network, which includes a basestation and node elements arranged in a hierarchical manner to show asupervisory or partially supervisory relationship between base and thenetwork node elements, and between the network node elements themselves.

FIG. 4 shows an exemplary method for supervising a network node element,in which a first device is provided to supervise the network nodeelement and a second device is provided to partially supervise thenetwork node element.

DETAILED DESCRIPTION

FIG. 1 shows exemplary network node elements A and B of a wirelessnetwork, in which network node element A supervises network node elementB. In this regard, to supervise network node element B, network nodeelement A may periodically poll network node element B and receive anacknowledgement with the status of network node element B. If networknode element A and network node element B are part of a multihop system,then network node element A may be supervised by another node element.

FIG. 2 shows an exemplary multihop network, which includes a basestation BS and node elements 1 through 11 arranged in a hierarchicalmanner, where a solid line (also referred to as an edge) connecting twonetwork node elements indicates a supervisory relationship between thetwo element nodes. In particular, the base station BS is configured tosupervise node elements 1, 2, 3, and 11, node element 1 is configured tosupervise node elements 4, 5 and 6, and node element 2 is configured tosupervise node elements 7, 8, 9 and 10. Node elements 3 and 11 are notconfigured to supervise other node elements.

The base station BS and node elements 1 through 11 of FIG. 2 form amultihop system. In this regard, node elements 1, 2, 3 and 11 may bereferred to as “hop 1” nodes, and node elements 4 through 10 may bereferred to as “hop 2” nodes. Hence, in FIG. 2 the base station BSsupervises the hop 1 nodes, and the hop 1 nodes supervise the hop 2nodes.

According to an exemplary embodiment and/or exemplary method of thepresent invention, to supervise node elements 4, 5 and 6, node element 1polls and/or listens for the status of each of the node elements 4, 5and 6, and passes the status of each node element to the base stationBS. Now, if node element 1 fails, the base station BS will not benotified by node element 1 of the status of node elements 4, 5 and 6.Redundancy in supervision may be provided to accommodate for the failureof node element 1, but if an additional node element is provided tosupervise these node elements additional resources may be consumedduring normal operation if node element 1 does not fail. For example, ifan additional node element is provided to supervise node elements 4, 5,and 6, and if node element 1 does not fail, then during normal operationthe status of each node element 4, 5, and 6 is passed twice to the basestation BS—once by node element 1 and once by the additionally providedsupervising node element.

In wireless systems, it may be assumed that transmitting is usually more“energy hungry” than receiving so that on average more energy may berequired to transmit messages than to receive messages. It also may beassumed that more than one node element can hear every node element, andthat every supervising node element can distinguish an “OK” status froma “NOT OK” status. So, for an energy constrained system the followingarrangement may be more efficient.

FIG. 3 shows an exemplary multihop network, which includes a basestation BS and node elements 1 through 11 arranged in a hierarchicalmanner, where a solid line connecting two network node elements (alsoreferred to as an “edge”) indicates a supervisory relationship betweenthe node elements, and a dotted line connecting two node elementsindicates a partial supervisory relationship between the node elements.In particular, solid lines connecting the base station BS and nodeelements 1, 2, 3 and 4 indicates that the base station BS supervisesnode elements 1, 2, 3 and 11, solid lines connecting node element 1 andnode elements 4, 5 and 6 indicate that node element 1 supervises nodeelement 4, 5 and 6, and solid lines between node element 2 and nodeelements 7, 8, 9 and 10 indicate that node element 2 supervises nodeelements 7, 8, 9 and 10. Moreover, dotted lines connecting node element11 and node elements 4 and 5 indicate that node element 11 partiallysupervises node elements 4 and 5, dotted lines connecting node element 1and node elements 7 and 8 indicate that node element 1 partiallysupervises node elements 7 and 8, and dotted lines connecting nodeelement 3 and node elements 9 and 10 indicate that node element 3partially supervises node elements 9 and 10. Here again, it is notedthat the base station BS and node elements 1 through 11 form a multihopsystem. In this regard, node elements 1, 2, 3 and 11 may be referred toas “hop 1” nodes, and node elements 4 through 10 may be referred to as“hop 2” nodes. Hence, in addition to supervising certain hop 2 nodes asindicated by solid lines, the hop 1 nodes each also partially supervisecertain other hop 2 nodes as indicated by dotted lines.

Since wireless media may be implemented as a broadcast media, having anadditional device that partially supervises a device, which is fullysupervised by another device, may be energy efficient. In this regard,the additional device does not poll or react to acknowledgments of itspartially supervised nodes or forward any “OK” status from the partiallysupervised nodes. Instead, the additional device may react when a nodeit partially supervises fails to send its “OK” status at the appropriatetime. For example, in FIG. 3, node element 1 partially supervises nodeelements 7 and 8. Accordingly, when node element 2 polls node element 7,node element 1 is also listening, and when node 7 acknowledges with thestatus, node element 1 is also listening. If node element 1 hears an“OK” status from node element 7, it does not take any action (i.e., itdoes not inform the base station BS about the status of node element 7).However, if node element 1 does not hear an “OK” status from nodeelement 7, it informs “NOT-heard” status to the base station BS whenpolled.

In this regard, since node element 1 is not polling node element 7, itdoes not spend extra energy to transmit. Therefore, since the nodeelements are expected to be normally in “OK” status, most of the timenode element 1 does not send extra data to the base station BS.Accordingly, energy is conserved. Furthermore, if node element 1 appendsthe status regarding the node elements it partially supervises to amessage it would otherwise send to the base station BS there may be noneed for additional communication. Moreover, additional redundancy maynot be required since if node element 2 fails or if the communicationbetween the base station BS and node element 2 is bad, the status ofnode elements 7 and 8 (and subtrees below node elements 7 and 8) isstill forwarded. Moreover still, the link from node element 1 to nodeelement 7 need not be bi-directional, that is, only node element 1 maybe required to hear node element 7 so that it may be non-critical ifnode element 7 cannot hear node element 1. Although, extra energy may bespent by node element 1 to listen to node element 7, depending on thetransceiver this may be minimal. Should node element 7 fail, extra bytesof information may be sent to the base station BS.

FIG. 4 shows an exemplary method 400 for supervising a network nodeelement, in which a first device is provided to supervise the networknode element and a second device is provided to partially supervise thenetwork node element. In this regard, the network node element may be,for example, a wireless sensor node.

In steps S401 and S401, the first device is provided to supervise thenetwork node element, and the second device is provided to partiallysupervise the network node element. In this regard, the first and seconddevices may be, for example, other network node elements, which arearranged in a hierarchical manner to receive messages from the networknode element and forward, if required, the messages to other networknode elements.

In steps S403 and S404, the first device polls the status of the networknode element, and the second device forwards the message from thenetwork node element to a higher level node if the message is an errormessage and if the first device does not forward this error message tothe higher level node. In this regard, the second device ignoresnon-error messages from the network node element, or error messages thathave been already forwarded to the higher level node by the firstdevice.

According to an exemplary embodiment and/or exemplary method of thepresent invention, the reporting of status by network nodes may beaggregated so that less overall data may be transmitted in the network,transmission energy and/or bandwidth may be saved, and the packet sizeof the transmission between nodes at different levels of the treehierarchy may not unnecessarily increase in an exponential manner. Forexample, node element 1 of the exemplary multihop network of FIG. 3,which supervises node elements 4 and 5, and partially supervises nodeelements 7 and 8, may aggregate the reporting of status of node elements4 and 5 collectively rather than individually (node element may alsoaggregate the reporting of status of node elements 7 and 8 since thestatus of partially supervised nodes may also be aggregated).Accordingly, when node element 1 reports an “OK” status to a higherlevel node it is interpreted that node element 1 and all node elementswithin its subtree and below (i.e., node elements 4 and 5) have an “OK”status. In this regard, since a node element may be supervised by morethan one node element (e.g., two node supervising node elements—one nodeelement to fully supervise and one node element to partially supervise)an inconsistency in reporting data may arise in which conflictinginformation regarding a particular node element is sent by two nodeelements assigned to supervise the same node element. For example, inFIG. 3, node element 7 is partially supervised by node element 1 andfully supervised by node element 2. It may occur, for example, that nodeelement 1 does not receive a status indication from node element 7, inwhich case node element 1 reports “NOT HEARD” with respect to the statusof node element 7, whereas node element 2, by contrast, does receive an“OK” status indication from node element 7 and therefore reports “OK”.In this instance, where conflicting information is received about nodeelement 7, the higher level node element will assume that thecommunication link between node element 1 and node element 7 is notfunctioning as well as the communication link between node element 2 andnode element 7 so therefore an “OK” status of node element 7 and itssubtree is also assumed. Likewise if the situation were reversed andnode element 1 received an “OK” status from node element 7, and nodeelement 2 did not receive status from node element 7, the higher levelnode element will assume that the communication link between nodeelement 2 and node element 7 is less functional that the communicationslink between node element 1 and node element 7 so therefore an “OK”status of node element 7 and its subtree is again assumed. Accordingly,in general, an “OK” status is accepted if at one of the node elementsassigned to supervise the particular node element reports an “OK”status. Also, should node element 1 report a “NOT HEARD” status withrespect to node element 7, and node element 2 reports a “SENSOR FAULTY”status then the “SENSOR FAULTY” status is assumed.

1. An apparatus to supervise a network, comprising: a first device tosupervise a network node element; and a second device to partiallysupervise the network node element.
 2. The apparatus of claim 1, whereinthe second device forwards an error message transmitted by the networknode element to a higher level node in the network if the first devicedoes not forward the error message.
 3. The apparatus of claim 2, whereinthe second device ignores non-error message from the network nodeelement.
 4. The apparatus of claim 2, wherein the second device appendsthe error message to a another message.
 5. The apparatus of claim 2,wherein at least one of the first device, the second device, the networknode element, and the higher level are energy constrained devices. 6.The apparatus of claim 2, wherein at least one of the first devices, thesecond device, the network node element, and the higher level node areenergy constrained wireless devices.
 7. The apparatus of claim 2,wherein the second device is configured to supervise another networknode element.
 8. The apparatus of claim 2, wherein the first device isconfigured to partially supervise another network node element.
 9. Themethod of claim 2, wherein the second device is configured to superviseanother network node element and the first device is configured topartially supervise the another network node element.
 10. A method ofsupervising a network node element, comprising: providing a first deviceto supervise a network node element; and providing a second device topartially supervise the network node element,
 11. The method of claim10, further comprising: polling, by the first device, a status of thenetwork node element; and forwarding, by the second device, an errormessage transmitted by the network node element to a higher level nodein the network if the first device does not forward the error message.12. The method of claim 11, further comprising: ignoring, by the seconddevice, non-error messages from the network node element.
 13. The methodof claim 11, further comprising: appending, by the second device theerror message to another message.
 14. The method of claim 11, wherein atleast one of the first device, the second device, the network nodeelement, and the higher level are energy constrained devices.
 15. Themethod of claim 11, wherein at least one of the first devices, thesecond device, the network node element, and the higher level node areenergy constrained wireless devices.
 16. The method of claim 11, whereinthe second device is configured to supervise another network nodeelement.
 17. The method of claim 11, wherein the first device isconfigured to partially supervise another network node element.
 18. Themethod of claim 11, wherein the second device is configured to superviseanother network node element and the first device is configured topartially supervise the another network node element.
 19. The method ofclaim 11, further comprising: aggregating, by at least one of the firstdevice and the second device, non-error messages from the network nodeelement and other network node elements within a subtree of the network.20. A method of supervising a network node element, comprising:providing a first device to supervise a network node element; providinga second device to partially supervise the network node element;polling, by the first device, a status of the network node element;aggregating, by the first device, non-error messages from the networknode element; forwarding, by the second device, an error messagetransmitted by the network node element to a higher level node in thenetwork if the first device does not forward the error message;appending, by the second device, the error message to another message;and ignoring, by the second device, non-error messages from the networknode element; wherein at least one of the first device, the seconddevice, the network node element, and the higher level are energyconstrained wireless devices.